A liquid fertilizer production apparatus is provided to produce a homogeneous liquid fertilizer having less stench and fewer pollutants by using a filtering material such as sawdust or chaff. A liquid fertilizer production apparatus includes: a stirring tank(20) having a filtering material inlet(22), a manure inlet(24), a stirring chamber(21) for stirring the filtering material and manure, a filtering material outlet, and a liquid fertilizer outlet for discharging a liquid fertilizer extracted from the stirred material of the filtering material and manure; an agitator(50) which is installed in the stirring chamber and stirs the filtering material and manure; a liquid fertilizer discharge device which discharges the liquid fertilizer into the outside; a filtering material discharge door(71) which opens and closes the filtering material outlet; and a solid-liquid separator(40) which is installed at the manure inlet so as to separate out solid manure from the manure charged into the manure inlet and put only liquid manure into the manure inlet. Further, the solid-liquid separator comprises a solid-liquid net for passing only liquid manure in the inputted manure and a shaker for shaking the solid-liquid net.